The security aspect of index coding has been studied in [1]}, [2]}, [3]}, [4]}, where in addition to the legitimate receivers there is an eavesdropper, and the server must simultaneously satisfy the receivers' decoding requirements and protect the messages from being decoded by the adversary.
An alternative setup where there is no external eavesdropper and the security constraints are against the receivers themselves, has been briefly discussed in [1]} and later studied in [6]}, [7]}.
